Help Biasing precision rectifiers

I've spent so much time trying to figure this out myself, but I can't

I'm currently using an LM324 op amp, and need to rectify a signal that has a negative peak of 0V and positive of either 2V, or 12V(which ever is easier)

I'll be using this in a car, so my supply voltage is 12V and 0v. I've spent the past 4 hours trying to figure out how to get a precision rectifier to work, and have came up with absolutely nothing.

I've tried all of the rectifiers on this site. **broken link removed**

I think I am having trouble with modifying these circuits to work on an all positive input signal. If anyone could suggest a precision rectifier that would work, and also tell me which values I should be using for the resistors, I'd appreciate it A loT!

Your input never goes negative so why do you need a rectifier circuit?
The circuits you found all have their input going positive and negative. Most use a positive and negative supply.

If I use the signal that is 0V to 12V Peak to peak, I want "ground" to be set at 6V, then have the negative alternation from 6V to 0V be rectified.

Now I would have an all positive signal that will be able to drive a load (LED's) with a very high duty cycle, instead of just less than 50% making them appear dim.

You can bias the precision rectifier at +6V to do almost what you want. But the LM324 opamp max output high is about 1V less than its supply voltage.

If your current requirement is not to high could you not use a 6 volt zener diode to rectify it?